> -----Original Message-----
> From: Ananyev, Konstantin
> Sent: Thursday, November 1, 2018 6:48 AM
> To: Xing, Beilei <beilei.x...@intel.com>; Zhang, Qi Z <qi.z.zh...@intel.com>
> Cc: dev@dpdk.org; sta...@dpdk.org
> Subject: RE: [dpdk-dev] [PATCH v3] net/i40e: fix Rx instability with vector
> mode
>
>
> Hi
>
> >
> > Previously, there is instability during vector Rx if descriptor number
> > is not power of 2, e.g. process hang and some Rx packets are
> > unexpectedly empty. That's because vector Rx mode assumes Rx
> > descriptor number is power of 2 when doing bit mask.
> > This patch allows vector mode only when the number of Rx descriptor is
> > power of 2.
> >
> > Fixes: 8e109464c022 ("i40e: allow vector Rx and Tx usage")
> > Fixes: a3c83a2527e1 ("net/i40e: enable runtime queue setup")
> > Cc: sta...@dpdk.org
> >
> > Signed-off-by: Beilei Xing <beilei.x...@intel.com>
> > ---
> > v3 changes:
> > - Add branch for non-first queue during runtime queue setup.
> > - Use function rte_is_power_of_2().
> > - Configure rx_vec_allowed during setting Rx function.
> > v2 changes:
> > - rx_vec_allowed is global configuration, avoid overwrite.
> >
> > doc/guides/nics/i40e.rst | 7 +++++++
> > drivers/net/i40e/i40e_rxtx.c | 30 +++++++++++++++++++++++++++---
> > 2 files changed, 34 insertions(+), 3 deletions(-)
> >
> > diff --git a/doc/guides/nics/i40e.rst b/doc/guides/nics/i40e.rst index
> > ab3928a..bfacbd1 100644
> > --- a/doc/guides/nics/i40e.rst
> > +++ b/doc/guides/nics/i40e.rst
> > @@ -172,6 +172,13 @@ Runtime Config Options
> >
> > -w 84:00.0,use-latest-supported-vec=1
> >
> > +Vector RX Pre-conditions
> > +~~~~~~~~~~~~~~~~~~~~~~~~
> > +For Vector RX it is assumed that the number of descriptor rings will
> > +be a power of 2. With this pre-condition, the ring pointer can easily
> > +scroll back to the head after hitting the tail without a conditional
> > +check. In addition Vector RX can use this assumption to do a bit mask
> using ``ring_size - 1``.
> > +
> > Driver compilation and testing
> > ------------------------------
> >
> > diff --git a/drivers/net/i40e/i40e_rxtx.c
> > b/drivers/net/i40e/i40e_rxtx.c index a827456..771193a 100644
> > --- a/drivers/net/i40e/i40e_rxtx.c
> > +++ b/drivers/net/i40e/i40e_rxtx.c
> > @@ -1735,12 +1735,21 @@ i40e_dev_rx_queue_setup_runtime(struct
> rte_eth_dev *dev,
> > * i40e_set_rx_function.
> > */
> > ad->rx_bulk_alloc_allowed = true;
> > - ad->rx_vec_allowed = true;
> > dev->data->scattered_rx = use_scattered_rx;
> > if (use_def_burst_func)
> > ad->rx_bulk_alloc_allowed = false;
> > + /**
> > + * Vector mode is allowed only when number of Rx queue
> > + * descriptor is a power of 2.
> > + */
> > + ad->rx_vec_allowed = rte_is_power_of_2(rxq->nb_rx_desc);
>
> Actually do we need to do it here?
> We call set_rx_function() anyway, it would do that check for us, wouldn't it?
>
> > i40e_set_rx_function(dev);
> > return 0;
> > + } else if (ad->rx_vec_allowed && !rte_is_power_of_2(rxq->nb_rx_desc))
> {
> > + PMD_DRV_LOG(ERR, "Vector mode is allowed, but descriptor"
> > + " number %d of queue %d isn't power of 2",
> > + rxq->nb_rx_desc, rxq->queue_id);
> > + return -EINVAL;
> > }
> >
> > /* check bulk alloc conflict */
> > @@ -2948,11 +2957,26 @@ i40e_set_rx_function(struct rte_eth_dev *dev)
> > {
> > struct i40e_adapter *ad =
> > I40E_DEV_PRIVATE_TO_ADAPTER(dev->data->dev_private);
> > + struct i40e_rx_queue *rxq;
> > uint16_t rx_using_sse, i;
> > + uint16_t desc;
>
> Please add empty line between var definitions and start of code.
> Helps readability.
>
> > /* In order to allow Vector Rx there are a few configuration
> > * conditions to be met and Rx Bulk Allocation should be allowed.
> > */
> > if (rte_eal_process_type() == RTE_PROC_PRIMARY) {
> > + if (!dev->data->dev_started) {
> > + for (i = 0; i < dev->data->nb_rx_queues; i++) {
> > + rxq = dev->data->rx_queues[i];
> > + desc = rxq->nb_rx_desc;
> > + if (!i)
queue_setup is not necessary start from queue 0, we can setup queue at any
order, so we can't assume i=0 is the first queue to setup.
And also we need to check if (dev->data->rx_queues[i] == NULL) to avoid segment
fault, since some queue may never be setup yet.
> > + ad->rx_vec_allowed =
> > + rte_is_power_of_2(desc);
> > + else if (ad->rx_vec_allowed &&
> > + !rte_is_power_of_2(desc))
> > + ad->rx_vec_allowed = false;
>
> Wouldn't be a bit cleaner:
> ad->rx_vec_allowed = (ad->rx_vec_allowed == true) ?
> ad->rte_is_power_of_2(desc)) : ad->rx_vec_allowed;
>
> > + }
> > + }
> > +
>
> Probably better to move that code into
> i40e_rx_vec_dev_conf_condition_check()
> that will be called on next line?
>
> > if (i40e_rx_vec_dev_conf_condition_check(dev) ||
> > !ad->rx_bulk_alloc_allowed) {
> > PMD_INIT_LOG(DEBUG, "Port[%d] doesn't meet"
> > @@ -2961,10 +2985,10 @@ i40e_set_rx_function(struct rte_eth_dev *dev)
> >
> > ad->rx_vec_allowed = false;
> > }
> > +
> > if (ad->rx_vec_allowed) {
> > for (i = 0; i < dev->data->nb_rx_queues; i++) {
> > - struct i40e_rx_queue *rxq =
> > - dev->data->rx_queues[i];
> > + rxq = dev->data->rx_queues[i];
> >
> > if (rxq && i40e_rxq_vec_setup(rxq)) {
> > ad->rx_vec_allowed = false;
> > --
> > 2.5.5
